As the fifth wave is settling in Hong Kong, Rapid at home tests have become a must have item for every household. Can we rely on them to be accurate indicators of infection? How can you tell the difference between a ‘good’ and ‘bad’ test kit?
The difference between A rapid antigen Test and a PCR test
The test kits you can buy from the pharmacy are all rapid antigen test kits, where as the ones used by most governmental labs are PCR (Polymerase Chain Reaction) tests. The Rapid Antigen test kits react to the Spike Protein found on the surface of the virus, the more virus detected, the greater the test kit will react to the sample.
This is typically shown as a deep red line on the T section of a test kit. This is why it is important to look closely at the T line, even a very faint line means a positive test.
The Rapid Antigen test however needs a substantial viral load to produce a positive result. It is possible that you are infected and produce a negative result if your viral load is small. The PCR test on the other hand uses a different method to test the presence of Covid 19. To make things simple, the PCR test copies any genetic material inside a sample millions of times, meaning even a trace of Covid 19 genetic data can be detected. The drawback of the PCR test is that it must be done in a lab and it takes far longer than the rapid antigen test.
Is there any point to the Rapid Test?
A positive result from the rapid test is a clear indicator that you are infected. If you are feeling unwell, a rapid test is the easiest and most effective way to tell if you have contracted covid 19.
If used correctly, the rapid test is also an effective way to test yourself if you fear you may have come into close contact, of for any other reason. It is important however to get the right kit, and to use it properly.
How to effectively choose and use a rapid test kit.
Many people are stressing on the perceived effectiveness of a kit. In reality, as long as you have purchased your kits from a reputable supplier, the biggest impact to test accuracy is in the execution of the test, not the printed test sensitivity. That being said, not all kits are made the same.
Choose a test kit that comes with an internal nasal (nasopharyngeal) swab.
The main difference you should be aware of in test kits is how they instruct you to retrieve a sample. The best kits will get their sample from your internal nasal cavity. The internal cavity will hold the most viral load, increasing the chance that a test kit will give an accurate result. Your nostril or oral cavity have a lesser viral load, so any test kit that is equipped to only collect samples from these locations will inherently have reduced sensitivity.
The easiest way to tell if your test kit is equipped to take a sample from your internal nasal cavity is the box length. As the swab needed for such a test is over 14cm long, the box that holds the test needs to be that long too. Of course, the box should also say ‘nasopharyngeal’ test, or contains a ‘nasopharyngeal’ swab.
Ensure that you collect a good sample.
Once you have located a nasopharyngeal test kit, you have to be sure that you use it correctly.
- Ensure that you are reaching deep into your nasal cavity. It should feel uncomfortable and make you want to sneeze.
- Move the swab around inside your nasal cavity. Spin and move the swab gently around inside your nasal cavity to collect as much mucus as possible.
- Swab both nostrils.
- Place the swab inside the provided tube and saturate the solution. Spin the swab inside the solution and rub it against the sides of the tube to ensure complete saturation.
- Gently squeeze the tip of the swab inside the tube. This will also help to ensure that your sample has the largest viral load potential.
Test more than once.
Especially if you think you have been in close contact, it is worth testing once a day over the course of 5 days. This reduces your chance for false negatives, and also allows any potential viral load to build up in your system if you are infected.
What to do if you test positive.
Test again immediately with another test to ensure that it is not a false positive, then follow the instructions of what your local government has outlined in the case of a positive test. While if you are asymptomatic, there may not be an immediate rush, it is very important to seek medical assistance with urgency if you feel any change in your ability to breath.
In the meantime, it is always best to prevent any possible infections with a high-quality mask. At Airizy, our masks are designed by PHD microbiologists to ensure that they are safe, then customized by you to suit your individual style. Shop here.